What meds cause melanosis coli?

October 8, 2025 •

4 min read

A significant majority, approximately 95%, of diagnosed cases of melanosis coli are linked to the prolonged use of anthraquinone-containing laxatives. We explain exactly what meds cause melanosis coli and how to reverse this common, benign colon pigmentation.

Quick Summary

Chronic use of anthraquinone laxatives such as senna and aloe can cause melanosis coli, a benign discoloration of the colon lining. This condition is reversible upon stopping the medication.

Key Points

Primary Cause: Long-term use of anthraquinone laxatives like senna, cascara, and aloe is the main driver of melanosis coli.
Mechanism: The condition is caused by the accumulation of lipofuscin pigment in the colon's macrophages, a result of cellular damage from anthraquinones.
Reversibility: Melanosis coli is benign and reversible; the discoloration typically resolves within 6 to 12 months after discontinuing the causative laxative.
Symptom-Free: The condition itself does not cause symptoms and is usually an incidental finding during a colonoscopy.
Alternative Treatments: Safer alternatives for managing chronic constipation include lifestyle changes, increased fiber intake, and non-anthraquinone laxatives.
Diagnosis: The diagnosis is confirmed during a colonoscopy and can be visually identified by the characteristic snake-like mucosal pigmentation.

The Primary Culprits: Anthraquinone Laxatives

Melanosis coli is a benign condition characterized by dark brown or black discoloration of the large intestine's inner lining. The primary culprits are stimulant laxatives that contain anthraquinones. These compounds are found naturally in certain plants and herbs and are commonly used in both over-the-counter and herbal constipation remedies. The pigmentation results from a process triggered by the long-term use of these laxatives, often over several months.

The following are the most common anthraquinone-containing medications and remedies associated with melanosis coli:

Senna: One of the most frequently cited causes, senna is a widely available stimulant laxative.
Cascara Sagrada: This natural bark derivative is also a potent anthraquinone stimulant.
Rhubarb: Used in traditional remedies and some commercial products, rhubarb contains anthraquinone compounds.
Aloe Latex: The bitter, yellow sap found just beneath the outer skin of the aloe leaf contains anthraquinones and is used as a laxative.
Buckthorn: Both Rhamnus and Frangula are types of buckthorn that contain these compounds and are used in herbal remedies.

The Mechanism Behind the Discoloration

Melanosis coli is often mistakenly thought to be related to melanin, the pigment responsible for skin color. However, the dark discoloration of the colon is caused by the accumulation of a different pigment called lipofuscin. The process is a fascinating and specific example of a drug side effect at the cellular level.

Cellular Process of Pigment Accumulation

Anthraquinone Activation: When anthraquinone laxatives are ingested, they remain in an inactive form until they reach the large intestine.
Cellular Apoptosis: Bacteria in the colon convert the inactive anthraquinones into active forms. These active compounds have a damaging effect on the epithelial cells lining the colon, prompting them to undergo a process of programmed cell death, known as apoptosis.
Phagocytosis: As the epithelial cells die, they break down into cellular debris. The immune system's macrophages, specialized cells that clean up cellular waste, then engulf these fragments.
Lipofuscin Deposition: Inside the macrophages, the cellular debris containing lipids and proteins is processed, leading to the formation and accumulation of lipofuscin pigment.
Pigmentation: The pigment-laden macrophages accumulate in the lamina propria, the connective tissue layer just below the surface epithelium, leading to the characteristic dark brown or black pigmentation seen during a colonoscopy.

Medications and Alternatives: A Comparison Table

When managing constipation, it is important to distinguish between anthraquinone laxatives and safer, non-pigmenting alternatives. The following table highlights the difference between these types of remedies.


Feature	Anthraquinone Laxatives (e.g., Senna, Cascara)	Non-Anthraquinone Alternatives (e.g., Psyllium, PEG)
Action	Stimulate nerve endings in the colon to cause muscular contractions and rapid transit.	Add bulk and moisture to stool, or draw water into the colon to soften stool.
Mechanism of Melanosis	Induce apoptosis of colon cells, leading to lipofuscin deposition in macrophages.	No association with colonic epithelial cell damage or pigmentation.
Associated Condition	Primary cause of melanosis coli with chronic use (>2 weeks).	No risk of causing melanosis coli.
Reversibility	Melanosis coli is reversible, but can take 6–12 months after stopping the laxative.	Not applicable, as they do not cause the condition.
Best for Use	Short-term relief for occasional constipation under medical supervision.	Chronic management of constipation and general bowel health.

Less Common Medication-Related Factors

While anthraquinone laxatives are the main cause, other medications and substances have been reported to potentially contribute to melanosis coli or similar pigmentation issues, though these are much rarer and less consistently linked.

Anthralin: A topical cream used to treat psoriasis has been anecdotally associated with intestinal melanosis after long-term use.
Nonsteroidal Anti-inflammatory Drugs (NSAIDs): Some studies have suggested a link, positing that NSAIDs can also induce mucosal cell apoptosis.
Bisacodyl: In some isolated reports, long-term use of this stimulant laxative has been mentioned as a potential factor.

It is crucial to note that the link between these non-anthraquinone substances and melanosis coli is not as well-established or prevalent as the link with anthraquinone laxatives.

Diagnosis and Management

Since melanosis coli has no specific symptoms of its own, it is almost always an incidental finding during a colonoscopy performed for other reasons, such as investigating the underlying constipation or screening for polyps. The dark pigmentation is a telltale sign for gastroenterologists.

The primary management strategy is straightforward: discontinuation of the causative anthraquinone laxative. The colon can take several months to a year to return to its normal color after stopping the medication. For long-term management of constipation, healthcare providers will recommend lifestyle changes and non-anthraquinone alternatives.

Conclusion

Melanosis coli is a common, harmless, and reversible side effect primarily caused by the chronic use of anthraquinone stimulant laxatives. While disconcerting in appearance, it poses no serious health threat and is not linked to colon cancer. Patients experiencing constipation are advised to work with their healthcare provider to identify and use safer, long-term alternatives like fiber supplements and osmotic laxatives, rather than relying on anthraquinone-containing products. The key to preventing and reversing this condition lies in informed medication choices and a shift toward healthy lifestyle modifications for bowel regularity.

For more information on digestive health and medication side effects, a good resource is the National Institutes of Health. https://www.ncbi.nlm.nih.gov/books/NBK493146/

Frequently Asked Questions

The most common medications causing melanosis coli are stimulant laxatives containing anthraquinones, including senna, cascara sagrada, aloe latex, and rhubarb.

No, melanosis coli is a benign and harmless condition. It does not increase the risk of colon cancer or other serious bowel diseases.

Melanosis coli can develop within a few months of chronic use of anthraquinone laxatives. The pigmentation often becomes noticeable after 4 to 12 months.

Yes, melanosis coli is fully reversible. The discoloration will gradually fade once the causative anthraquinone laxative is stopped, though it may take 6 to 12 months for the colon to return to its normal color.

Melanosis coli itself is asymptomatic. Any symptoms experienced, such as constipation or abdominal discomfort, are typically from the underlying condition that led to laxative use.

Melanosis coli is typically an incidental finding during an endoscopic procedure, such as a colonoscopy. The gastroenterologist observes the characteristic dark pigmentation on the colon's lining.

For chronic constipation, it is best to use non-anthraquinone alternatives. These include increasing dietary fiber, staying hydrated, regular exercise, and using bulk-forming or osmotic laxatives like psyllium or polyethylene glycol.

Many herbal laxatives, such as those containing senna or rhubarb, contain anthraquinones and are not intended for long-term use. The chronic use of these products can lead to melanosis coli.